Yeah that one might work. And I only would like to use one powersource, which is 12 volts to run everything. Most stuff I have hooked up to my Arduino is 12 volts, but the RFID Reader is 5v-16v. Barely getting by with that. So that's why I would like 12 volts to also power the relays and other stuff.

That's what I'm wondering. How and where do I add the heatsink. And I'm driving the relays with 2n2222 transisters. And I'm using an Altronix 12 volts power source, so I think I'm good there. I'd be running the relays and RFID Reader off of it.